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Full text of "The manufacture and properties of iron and steel"

374
METALLURGY OF IRON AND STEEL.
tainty so narrow that it will be better to make a true average of the three values. There were 239 heats giving a value of 860: lb., 192 heats giving 940 lb., and 231 heats giving 1290 lb., so that the true average is 1033 lb. For the sake of simplicity the value of 0.01 per cent, of phosphorus will be taken as 1000 pounds.
In reducing to a zero-base, as in the last column of Table XVII-P, there will be certain errors, since the values of carbon and manganese are not inerrant; but the original classification into groups of about the same carbon minimizes the disturbing effect. Thus in Table XVII-P the first main division has five units; the highest carbon is 0.1540 per cent, and the lowest 0.1491 per cent,, a varia-
TABLE XVII-P.                !
Classification of Acid Heats According to Content of Phosphorus.
NOTE.—In the last column a value of 1,000 IDS. is given to 0.01 per cent, of cartoon; the figure for manganese is taken from Table XVII-R. Fig. XVII-B is plotted from the last column, but the data are combined to rectify the lines.
Limits of carbon ; per cent.	Number of heats.	Chemical composition.				Ultimate strength.	
		Carbon, per cent	Phosphorus ; per cent.	Manganese; percent.	Sulphur; per cent.	Actual records; pounds per sq. inch.	After deducting for carbon and manganese; pounds per sq.. inch.
0.075 to 0.224	39 54 38 61 47	0.1491 0.1524 0.1504 0.1528 0.1540	0.0396 0.0500 0.0557 0.0617 0.0717	0.439 0.430 0.441 0.445 0.443;	0.0539 0.0559 0.0568 0.0588 0.0623	59944 61038 61595 62633 63292	44616 45438 46063 46813 47328
0.225 to 0.374	46 53 44 49	0.3373 0.3317 0.3265 0.3120	0.0331 0.0438 0.0523 0.0626	0.514 0.537 0.527 0.537	0.0477 0.0539 0.0538 0.0537	79636 81231 81197 80390	42805 4,4,111 45194 45792
0.375 to 0.524	52 63 54 62	0.4413 0.4424 0.4366 0.4235	0.0271 0.0343 0.0404 0.0504	0.514 0.508 0.521 0.534	0.0437 0.0461 0.0494 0.0526	90413 . 91180 92215 91370	42270 43138 44320 44517
tion of 0.0049 per cent. Carbon has been Valued at 1000 lb. for 0.01 per cent., and if perchance that value is in error by 50 lb. the results determined from that division of the table will be wrong by only 50X0.49=25 lb. The last column shows a strength of 47,328 lb. for one base and 44,616 lb. for the other,' a difference of 2712 lb., so that the assumed error of 50 lb. in the value of carbon produces an error of only 1 per cent, in the value of phosphorus in this particular division. This argument applies also